How did I get a letter from my email?

Question

Mail server

Today I received a message from my email with a domain name.
The sender's name has been changed.
In Reply-To, mail-gmail was specified, a letter was sent through a proxy from Microsoft Outlook Express 6.00.2900.5931.
Was it in Microsoft Outlook that they found a way to send a message under the guise of someone else's email, or could the message be sent through a script added to my site?

Answer 1

Any mail client can send a letter with any return address.
and not only from the client.
The question is different. Why did your mail server calmly accept such a letter and did not regard it as spam?!

Answer 2

Yes, you can set any headers for me. All scripts on dozens of servers send me mail from my google email

Answer 3

Puma: RIGHT.
SERGEY: And how to do it - whoever chooses what, for example, you decided to show telnet.
and therefore I do not see anything unusual that the server of the questioner accepts this mail.
in order to consider that this is spam, at least one of the addresses (from, to whom) does not belong to the domain, and spam / non-spam analysis is carried out not by headings, but by analyzing them and the body of the letter.
TO THE AUTHOR: bring the settings (checks) of your MTA, plz, without this, there's nothing.

Answer 4

const splitArr = (arr, chunks) =>
  [...Array(chunks)].map((_, c) => arr.filter((n, i) => i % chunks === c));

or

const splitArr = (arr, chunks) =>
  arr.reduce((acc, n, i) => ((acc[i % chunks] = acc[i % chunks] || []).push(n), acc), []);

Answer 5

https://lodash.com/docs/4.17.15#chunk
_.chunk(array, [size=1])
Creates an array of elements split into groups the length of size. If array can't be split evenly, the final chunk will be the remaining elements.